Voltage line communications during pulse power drilling

ABSTRACT

A method of communication along a shared voltage line is disclosed. In pulse power drilling, a generator charges applies voltage to a shared voltage line, which capacitively charges electrodes for formation drilling. While the generator controls the charging rate, charge voltage, and post-delay time between the charging cycles, a pulse power controller determines the pre-delay time by firing electrodes to discharge the stored voltage. Communication from the pulse power controller to the generator is encoded in the pre-delay time, where pre-delay times longer than a minimum pre-delay time correspond to time bins with pre-determined communications between the pulse power controller and the generator. The generator can also communicate to the pulse power controller via manipulation of the post-delay time.

TECHNICAL FIELD

The disclosure generally relates to pulse power drilling, and to voltageline communications during pulse power drilling.

BACKGROUND

During pulse power drilling, communication among different components ofa drill string can be inhibited by the electrical power that isgenerated and transmitted along the drill string. Such power levels canresult in fluctuations in electric fields and mechanical oscillations.Also, pulse power drilling operations can cause vibrations that furthercomplicate electrical, mechanical, and optical signal transmissionbetween components downhole. Drill string components for pulse powerdrilling can also experience stress at joints and junctions betweencomponents, which can weaken communication and mechanical links betweenportions of the drill string.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the disclosure may be better understood by referencing theaccompanying drawings.

FIG. 1 depicts an example pulse power drilling assembly, according tosome embodiments.

FIG. 2 depicts a flowchart of example operations for voltage linecommunications from a pulse power controller to a generator during pulsepower drilling, according to some embodiments.

FIG. 3 depicts a graph of voltage over time for an example two bincommunication from pulse power controller to generator, according tosome embodiments.

FIG. 4 depicts a graph of voltage over time for an example four bincommunication from pulse power controller to generator, according tosome embodiments.

FIG. 5 depicts a flowchart of example operations for voltage linecommunications from a generator to a pulse power controller, accordingto some embodiments.

FIG. 6 depicts a graph of voltage over time for an example communicationfrom the generator to the pulse power controller, according to someembodiments.

FIG. 7 depicts a flowchart of example operations for voltage linecommunications between a pulse power controller and a generator usingadditive signals during pre-delay and post-delay time periods, accordingto some embodiments.

FIG. 8 depicts a graph of voltage over time for an example communicationin which a communication signal is embedded within the DC signal duringthe pre-delay or post-delay, according to some embodiments.

FIG. 9 depicts an example computer, according to some embodiments.

DESCRIPTION

The description that follows includes example systems, methods,techniques, and program flows that embody aspects of the disclosure.However, it is understood that this disclosure may be practiced withoutthese specific details. For instance, this disclosure refers tocommunication between a generator and a pulse power controller inillustrative examples. Aspects of this disclosure can be also applied tocommunication between a voltage supplier and a discharge controller thaton a shared voltage line. In other instances, well-known instructioninstances, protocols, structures, and techniques have not been shown indetail in order not to obfuscate the description.

In pulse power drilling, drilling can be based on periodic electricaldischarges from electrodes that cause formation destruction due toplasma formation, liquid vaporization, gas expansion due to temperaturechanges, vibration, and shockwave effects, etc. In various cases, therate and timing of charging and discharging can be adjusted due tochanges in drilling or formation conditions. For example, a rate of thecharging of capacitors in a next charge cycle can be increased if thebottom of the drilling assembly is not in contact with a bottom of theborehole.

In some embodiments, various components of the pulse power drillingassembly can communicate through a voltage line for transmission ofpower between components of the drilling assembly (instead of aconventional communication line).

In some implementations, the components communicating to each other viaa voltage line can include two different controllers (or computingdevices) at different longitudinal locations along the drillingassembly. For example, a first controller can be a generator controllerfor controlling a generator that generates the power to be used tocreate the periodic electrical discharges. A second controller can be apulse power controller for controlling the periodic emitting of theelectric discharges into the subsurface formation through one or moreelectrodes. In some implementations, the pulse power controller canencode a communication (regarding the charge time or rate of the nextcharge cycle) in the voltage line that is received and decoded by thegenerator controller. For example, the pulse power controller can encodethe communication by varying a time delay between a time when thecapacitors are considered fully charged and a time when the electricaldischarge occurs or a length of time over which the voltage issubstantially constant. As further described below, communication can bebidirectional between the components. For instance, the pulse powercontroller and the generator controller can communicate by adjusting ormodulating different time lengths and voltages along the shared voltageline. Additionally, different encoding techniques can be used forencoding communications on the voltage line.

For example, communications can be encoded in a length of the pre-delayprior to electrode discharge, the length of a post delay prior to thebeginning of a next charge cycle, voltage fluctuations during pre-delay,voltage fluctuations during post-delay, voltage levels, etc. Becausecommunications can leverage an existing voltage line, an additional lineor source of communication is not needed between certain components ofthe drilling assembly. Such embodiments can be used across a joint ofthe drilling assembly where two parts of the assembly are coupledtogether. For example, such embodiments can be used across a jointwherein the two parts are coupled together at the well site (i.e., afield joint). Using such embodiments across a joint can reducemechanical complexity and reduce the likelihood of a breakdown becausefewer electrical or other communication lines are required to passacross the joint.

Example System

FIG. 1 depicts an example pulse power drilling assembly, according tosome embodiments. FIG. 1 illustrates an example drilling apparatus 100,including a pulse power drilling assembly (hereinafter “assembly”) 150positioned in a borehole 106 and secured to a length of drill pipe 102coupled to a drilling platform 160 and a derrick 164. The assembly 150is configured to further the advancement of the borehole 106 using pulseelectrical power generated by the assembly 150 and provided toelectrodes 144 in a controlled manner to break up or crush formationmaterial of a subsurface formation along the bottom face of the borehole106 and in the nearby proximity to the electrodes 144.

The flow of drilling fluid (illustrated by the arrow 110A pointingdownward within the drill pipe 102) is provided from the drillingplatform 160, and flows to and through a turbine 116, exiting theturbine 116 and flowing on into other sub-sections or components of theassembly 150, as indicated by the arrow 110B. The flow of drilling fluidthrough the turbine 116 causes the turbine 116 to be mechanicallyrotated. This mechanical rotation is coupled to an alternatorsub-section or component of the assembly (hereinafter “alternator”) 118in order to generate electrical power. The alternator 118 can furtherprocess and controllably provide the electrical power to the rest of thedownstream assembly 150. The stored power can then be output from theelectrodes 144 in order to perform the advancement of the borehole 106via periodic electrical discharges.

The drilling fluid flows through the assembly 150, as indicated by arrow110B, and flows out and away from the electrodes 144 and back toward thesurface to aid in the removal of the debris generated by the breaking upof the formation material at and nearby the electrodes 144. The fluidflow direction away from the electrodes 144 is indicated by arrows 110 Cand 110 D. In addition, the flow of drilling fluid may provide coolingto one or more devices and to one or more portions of the assembly 150.In various embodiments, it is not necessary for the assembly 150 to berotated as part of the drilling process, but some degree of rotation oroscillations of the assembly 150 may be provided in various embodimentsof drilling processes utilizing the assembly 150, including internalrotations occurring at the turbine 116, in the alternator sub-section,etc.

As illustrated in FIG. 1 , the assembly 150 includes multiplesub-assemblies, including in some embodiments the turbine 116 at a topof the assembly 150 where the top of the assembly is a face of theassembly 150 furthest from a drilling face of the assembly 150 (whichcontains the electrodes 144). The turbine 116 is coupled to multipleadditional sub-sections or components. These additional sub-sections orcomponents may include various combinations of the alternator 118, arectifier 120, a rectifier controller 122, a direct current (DC) link124, a DC to DC booster 126, a generator controller 128, a pulse powercontroller 130, a switch bank 134, including one or more switches 138,one or more primary capacitors 136, a transformer 140, one or moresecondary capacitors 142, and the electrodes 144.

The assembly 150 can be divided into a generator 152 and a pulse powersection 154. The generator 152 can include the turbine 116, thealternator 118, the rectifier 120, the rectifier controller 122, the DClink 124, the DC to DC booster 126, and the generator controller 128.The pulse power section 154 can include the pulse power controller 130,the switch bank 134, the one or more primary capacitors 136, thetransformer 140, the one or more secondary capacitors 142, and theelectrodes 144. Component can be divided between the generator 152 andthe pulse power section 154 in other arrangements, and the order of thecomponents can be other than shown. The assembly 150 may be comprised ofmultiple sub-sections, with a joint used to couple each of thesesub-sections together in a desired arrangement to form the assembly 150.Field joints 112A-C can be used to couple the generator 152 and thepulse power section 154 to construct the assembly 150 and to couple theassembly 150 to the drill pipe 102. Embodiments of the assembly 150 mayinclude one or more additional field joints coupling various componentsof the assembly 150 together. Field joints may be places where theassembly 150 is assembled or disassembled in the field, for example atthe drill site. In addition, the assembly 150 may require one or morejoints referred to as shop joints that are configured to allow varioussub-sections of the assembly 150 to be coupled together (for example atan assembly plant or at a factory). For example, various components ofthe assembly 150 may be provided by different manufacturers, orassembled at different locations, which require assembly before beingshipped to the field.

Regardless of whether a joint in the assembly 150 is referred to as afield joint or a shop joint, the center flow tubing 114 extends throughany of the components that includes the center flow tubing 114. A jointbetween separate sections of the center flow tubing 114 or a hydraulicseal capable of sealing the flow of the drilling fluid within the centerflow tubing 114 may be formed to prevent leaking at the joints.

The flow of drilling fluid passing through the turbine 116 continues toflow through one or more sections of a center flow tubing 114, whichthereby provides a flow path for the drilling fluid through one or moresub-sections or components of the assembly 150 positioned between theturbine 116 and the electrodes 144, as indicated by the arrow 110Bpointing downward through the cavity of the sections of the center flowtubing 114. Once arriving at the electrodes 144, the flow of drillingfluid is expelled out from one or more ports or nozzles located in or inproximity to the electrodes 144. After being expelled from the assembly150, the drilling fluid flows back upward toward the surface through anannulus 108 created between the assembly 150 and the walls of theborehole 106.

The center flow tubing 114 may be located along a central longitudinalaxis of the assembly 150 and may have an overall outside diameter orouter shaped surface that is smaller in cross-section than the insidesurface of a tool body 146 in cross-section. As such, one or more spacesare created between the center flow tubing 114 and the inside wall ofthe tool body 146. These one or more spaces may be used to house variouscomponents, such as components which make up the alternator 118, therectifier 120, the rectifier controller 122, the DC link 124, the DC toDC booster 126, the generator controller 128, the pulse power controller130, the switch bank 134, the one or more switches 138, the one or moreprimary capacitors 136, the transformer 140, and the one or moresecondary capacitors 142, as shown in FIG. 1 . Other components may beincluded in the spaces created between the center flow tubing 114 andthe inside wall of the tool body 146. The center flow tubing 114 sealsthe flow of drilling fluid within the hollow passageways included withinthe center flow tubing 114 and at each joint coupling sections of thecenter flow tubing 114 together and prevent the drilling fluid fromleaking into or otherwise gaining access to these spaces between thecenter flow tubing 114 and the inside wall of the tool body 146. Leakageof the drilling fluid outside the center flow tubing 114 and within theassembly 150 may cause damage to the electrical components or otherdevices located in these spaces and/or may contaminate fluids, such aslubrication oils, contained within these spaces, which may impair orcompletely impede the operation of the assembly 150 with respect todrilling operations.

The drilling apparatus 100 can include one or more logging tools 148.The logging tools 148 are shown as being located on the drill pipe 102,above the assembly 150, but can also be included within the assembly 150or joined via shop joint of field joint to assembly 150. The loggingtools 148 can include one or more logging with drilling (LWD) ormeasurement while drilling (MWD) tool, including resistivity, gamma-ray,nuclear magnetic resonance (NMR), etc. The drilling apparatus 100 canalso include directional control, such as for geosteering or directionaldrilling, which can be part of the assembly 150, the logging tools 148,or located elsewhere on the drill pipe 102.

Communication from the pulse power controller 130 to the generatorcontroller 128 allows the pulse power controller 130 to transmit dataabout and modifications for pulse power drilling to the generator 152.Similar, communication from the generator controller 128 to pulse powercontroller 130 allows the generator 152 to transmit data about andmodifications for pulse power drilling to the pulse power section. Thepulse power controller 130 can control the discharge of the pulse powerstored for emissions out from the electrodes 144 and into the formation,into drilling mud, or into a combination of formation and drillingfluids. The pulse power controller 130 can measure data about theelectrical characteristics of each of the electrical discharges—such aspower, current, and voltage emitted by the electrodes 144. Based oninformation measured for each discharge, the pulse power controller 130can determine information about drilling and about the electrodes 144,including whether or not the electrodes 144 are firing into theformation (i.e. drilling) or firing into the formation fluid (i.e.electrodes 144 are off bottom). The generator 152 can control the chargerate and charge voltage for each of the multiple pulse power electricaldischarges. The generator 152, together with the turbine 116 andalternator 118, can create an electrical charge in the range of 16kilovolts (kV) which the pulse power controller 130 delivers to theformation via the electrodes 144.

When the pulse power controller 130 can communicate with the generator152, the generator 152 and the alternator 118 can ramp up and ramp downin response to changes or electrical discharge characteristics detectedat the pulse power controller 130. Because the load on the turbine 116,the alternator 118, and the generator 152 is large (due to the highvoltage), ramping up and ramping down in response to the needs of thepulse power controller 130 can protect the generator 152 and associatedcomponents from load stress and can extend the lifetime of components ofthe pulse power drilling assembly. If the pulse power controller 130cannot communicate with the generator 152, then the generator 152 mayapply a constant charge rate and charge voltage to the electrodes 144 orotherwise respond slowly to downhole changes—which would be the case ifthe generator 152 is controlled by the drilling mud flow rate adjustedat the surface or another surface control mechanism.

In instances where the assembly 150 is off bottom, electrical powerinput to the system can be absorbed (at least partially) by the drillingfluid, which can be vaporized, boiled off, or destroyed because of thelarge power load transmitted in the electrical pulses. In instanceswhere the assembly 150 is not operating correctly, such as when one ormore switch experiences a fault or requires a reset, application of highpower to the capacitors 136/142 or the electrodes 144 can damagecircuitry and switches when applied at unexpected or incorrect times. Inthese and additional cases, communications or messages between the pulsepower controller 130 and the generator 152 allow the entire assembly tovary charge rates and voltages, along with other adjustments discussedlater. Especially where the pulse power controller 130 and generator 152are autonomous, i.e. not readily in communication with the surface,downhole control of the assembly 150 can improve pulse power drillingfunction.

Example Operations

FIG. 2 depicts a flowchart of example operations for voltage linecommunications from a pulse power controller to a generator during pulsepower drilling, according to some embodiments. A flowchart 200 of FIG. 2includes operations described as performed by a controller or computerof the generator and by the pulse power controller for consistency withthe earlier description. Such operations can be performed by hardware,firmware, software, or a combination thereof. However, assemblycomponent naming, division, sub-section organization, program codenaming, organization, and deployment can vary due to arbitrary operatorchoice, assembly ordering, programmer choice, programming language(s),platform, etc. Additionally, operations of the flowchart 200 aredescribed in reference to the example drilling apparatus 100 of FIG. 1 .The flowchart 200 includes the operations of blocks 202, 204, 212, 214,216, and 218 as performed by the generator 152, and the operations ofblock 206, 208, and 210 as performed by the pulse power controller 130.One or more of the operations described as being performed by thegenerator 152 may be performed by one or more of the alternator 118, acontroller of the generator 152, or a processor of the generator 152.One or more of the operations described as being performed by the pulsepower controller 130 may instead be performed by a processor of thepulse power controller 130, or performed in concert with one or moreswitches of the pulse power controller 130.

FIG. 2 includes operations related to electrical charging anddischarging of capacitors or other electrical components whoseelectrical discharge is emitted out into the formation throughelectrodes 144. In some implementations, the generator 152 and the pulsepower controller 130 share a wired electrical connection or line(hereinafter “the voltage line”) that transfers voltage and current overa field joint (or any other type of joint or junction). The generator152 can control a voltage charging cycle, while the pulse powercontroller 130 can control the voltage discharge. By modifying variousparts of the charge and discharge cycle, the generator 152 and the pulsepower controller 130 can communicate data over the voltage line whilealso continuing to drill using periodic electric discharges beingdischarged from the electrodes 144.

At block 202, a charge cycle is initiated. For example, with referenceto the assembly 150 of FIG. 1 , a charge cycle can be initiated for thegenerator 152 and the pulse power controller 130. The generator 152 andthe pulse power controller 130 can have independent clocks or clocksthat are synched to one or more events of the charge cycle. Therefore,the start of the charge cycle—which is based on the end of the previouscharge cycle or the beginning of charging of the voltage line—can bemeasured as beginning at different times in the generator 152 and thepulse power controller 130. For a first charge cycle or a charge cyclefor which previous cycle data is not available, the charge cyclebeginning can be determined by the generator 152, which initiates afirst charging of the voltage line based on electrical charging via thealternator 118 by the turbine 116 which is controlled by drilling mudflow. A time difference between the beginning of a given charge cycle asmeasured by the generator 152 and the pulse power controller 130 is aresult of separate clocks and can further be confounded by measurementaccuracy. Because communication between the pulse power controller 130and the generator 152 is based on charge cycle characteristics and timelengths, communication times and measurements can be larger than clockerror or uncertainty or measurement resolution limits. Block 202 beginsa loop for each charge cycle that continues for the generator 152 atblock 204 and for the pulse power controller 130 at block 208.

At block 204, a charge rate and charge voltage for the current chargecycle are set. For example, with reference to the assembly 150 of FIG. 1, the generator 152 can set the charge rate and voltage for the currentcharge cycle. In some embodiments, the charge rate and charge voltagecan be iteratively adjusted by communication between the pulse powercontroller 130 and the generator 152 for each charge cycle. The currentcharge rate and charge voltage for a first cycle or any cycle for whichprevious cycle data is not available can be pre-programmed to correspondto a baseline or minimum charge rate (and maximum charge time) andcharge voltage commensurate with a ramp up cycle. For a subsequentcharge cycle, the charge rate and charge voltage can be determined bythe generator 152 based on the charge rate and charge voltage of theprevious cycle and any communication detected by the generator 152 fromthe pulse power controller 130.

At block 206, a shared voltage line is charged at the charge rate and tothe charge voltage set in block 204. For example, with reference to theassembly 150 of FIG. 1 , the generator 152 can charge the shared voltageline. For example, the generator 152 can apply the electric potentialgenerated by the turbine 116, the alternator 118, etc. to the sharedvoltage line that connects the generator 152 to the capacitors 136 orother electrical components of the pulse power section 154. From block206, flow continues to block 214.

At block 208, a determination of what communication is to be transmittedon the shared voltage line back to the generator is made. For example,with reference to the assembly 150 of FIG. 1 , the pulse powercontroller 130 can make this determination. For instance, based on theelectrical discharge characteristics of the previous cycle, the pulsepower controller 130 can determine that a communication needs to betransmitted back to the generator 152 regarding a modification to thecharge rate and charge voltage. Example communications sent from thepulse power controller 130 to the generator 152 can include: increasecharge rate, decrease charge rate, increase charge voltage, decreasecharge voltage, increase a post-delay time, decrease a post-delay time,initiate emergency shutdown, etc. The post-delay time can be defined asthe time between the electrical discharge of one discharge cycle and thecharging of the next cycle. In some embodiments, the number of differentcommunications that the pulse power controller 130 can select from tosend to the generator 152 can be determined by a minimum pre-delay time,a maximum pre-delay time, and a bin resolution. A pre-delay time can bedefined as the length of time between the end of the charging by thegenerator 152 (i.e. when the voltage line reaches the charge voltage)and the discharge of that voltage by the pulse power controller 130.During the pre-delay time, voltage on the voltage line can be relativelyconstant.

To illustrate, FIG. 3 depicts a graph of voltage over time for anexample two bin communication from pulse power controller to generator,according to some embodiments. FIG. 3 depicts a graph 300 displaying anexample plot of voltage (on a y-axis 302) of the voltage line as afunction of time (on an x-axis 304). The graph 300 of FIG. 3 isdescribed in reference to the example drilling apparatus 100 of FIG. 1 .A charging time 310 is depicted during which the generator 152 appliesincreasing voltage, i.e. charges, the voltage line connecting thegenerator 152 and the pulse power controller 130. A charging rate 314 isthe slope of the voltage curve during the charging time, which is acharge voltage 312 divided by the charging time 310 for a linear chargerate. A pre-delay time 320 is the time between when the voltage hasreached the charge voltage 312 and when the voltage is discharged by thepulse power controller 130 at a discharge time. A maximum pre-delay time328 can be defined as the maximum time the pulse power controller 130will allow voltage along the shared voltage line. This maximum pre-delaytime 328 can be necessary because periodic discharging of the electrodescan be required to protect components of the generator 152 that continueto generate electrical power which can overwhelm available locations tostore such power without such discharging. A minimum pre-delay time 322can be defined as the minimum time the pulse power controller 130requires to effectively determine that the generator 152 has stoppedcharging and to fire one or more switches 138 to generate the dischargeof the stored voltage. In this example, between the minimum pre-delaytime 322 and the maximum pre-delay time 328, two time bins are depicted.A first bin 324 and a second bin 326 can correspond to any assignedcommunication as programmed in the pulse power controller 130 and thegenerator 152.

The pre-delay time 320 for each cycle is measured from an inflectionpoint 332 where the charging time 310 ends and the voltage is steady atthe charge voltage 312. The pre-delay time 320 length falls in eitherthe first bin 324, where an example pre-delay time 334 is shown, or inthe second bin 326, where an example pre-delay time 336 is shown. Inthis example, the first bin 324 is shown as corresponding to an increasein charging rate and a decrease in charging time and the second bin 325is shown as corresponding to a decrease in charging rate and an increasein charging time. In one or more embodiments, different bin assignmentscould be used, such as bits 0 and 1, or bin orders could be reversed.Additionally, bins can be different time lengths as permitted byresolution uncertainty. A first bin can overlap with or include theminimum pre-delay time 322.

The pre-delay time 320 of the first cycle effects the charge rate of thesecond cycle, as shown. After discharge, a post-delay time 330 separatesthe beginning of the charging time of the second cycle from discharge ofthe first cycle. The post-delay time 330 allows electrical switches,such as the one or more switches 138, to be operated and ensures thatthe pulse power controller 130 has fully discharged the capacitors 136and 142 and protects the generator 152 and alternator 118 from powerload shocks. After the post-delay time 330, the generator 152 againcharges the voltage line at a second cycle charging rate. An increasedcharging rate 340 and a charging time decreased by interval 342 for thesecond cycle corresponds to a pre-delay time within the first bin 324 ofthe first cycle, while a decreased charging rate 350 and a charging timeincreased by interval 354 for the second cycle corresponds to apre-delay time within the second bin 326 of the first cycle. The changein the charging rate can be pre-programmed as a specific value (i.e. aΔV/s in volts per second), as a specific value for an increase and aspecific value for a decrease (i.e.ΔV/sec_(increase)≠ΔV/sec_(decrease)), a percentage change (e.g. ΔV/secis equal to one percent (1%) of the previous charging rate), apercentage change for an increase and a percentage change for a decrease(e.g. ΔV/sec_(increase) is 1% of the previous charging rate andΔV/sec_(decrease) decrease is 5% of the previous charging rate), etc. Inone or more embodiments, the change in the charging rate can bepre-programmed as a change in the charging time 310. In one or moreembodiments, the change in the charging time 310 can be pre-programmedas a specific value (i.e. ±1 millisecond (ms)), a percentage change(e.g. Δt_(charging) is equal to 1% of t_(charging)), or different valuesfor time increases and time decreases.

The increased charging rate 340 means that the generator 152 reaches thecharge voltage 312 at an earlier time that it would if the charging ratewere unchanged. The decreased charging rate 350 means that the generator152 reaches the charge voltage 312 at a later time than it would if thecharging rate was unchanged. The pre-delay time of the second cyclelikewise effects the charging rate of a third cycle (not shown), and soforth. In one or more embodiments, the generator 152 can treat acommunication to change the charging rate as a communication to alsoadjust the post-delay time 330 in order to maintain discharge of thecapacitors 136 and 142 as a pre-determined frequency.

In one or more embodiment, the first bin 324 and the second bin 326 caninstead be assigned to bit values. If the bins correspond to bit values,such as 0 and 1 or −1 and +1, the pulse power controller 130 cancommunicate one or more communication or modification to the generator152 over one or more charge cycles. For instance, the generator 152 candetermine that, if the bins correspond to bits 0 and 1, for an averagebit value greater than 0.5 the charge rate is increased, for an averagebit value less than 0.5 the charge rate is decreased, and for an averagebit value of 0.5 the charge rate is unchanged. In a similar manner,charge voltage 312 or post-delay time 330 can be adjusted.

The minimum pre-delay time 322 corresponds to a minimum length of timenecessary for the pulse power controller 130 to detect that thegenerator 152 has reached the charge voltage 312 and is no longercharging. The detection of a steady voltage can be complicated by thedifferent clocks by which time is measured at the generator 152 and thepulse power controller 130, and by the ability of the pulse powercontroller 130 to detect the point at which voltage is steady. Becausethe voltage can be large (for example, 16 kV) and the charging time 310fast (for example, 17 ms), the detection of the inflection point 332between charging voltage and steady state voltage can be complicated byany voltage overshoot or ripple. The pulse power controller 130 canmeasure and record voltage as a function of time and can detect when thecharging period ended and the pre-delay time 320 began by lookingbackwards over the recorded data.

The maximum pre-delay 328 time corresponds to a maximum length of timethat is allowed by the generator 152 and pulse power controller beforeinitiating a shutdown or failsafe mode, such as emergency off (EMO) orother protocol. The pulse power controller 130 and generator 152 caninclude a failsafe that triggers a shutdown of the generator 152, thealternator 118, and the turbine 116 and a discharge of the electrodes144 if the maximum pre-delay time 328 is reached. The maximum pre-delaytime 328 protects the assembly 150 from catastrophic overcharging ofelectrical components, such as the capacitors 136/142 and electrodes144. If, for example, the pulse power controller 130 switches 138 aremalfunctioning and the electrodes 144 are not discharging, in theabsence of the maximum pre-delay time 328 the pulse power controller 130would continue to charge until electrical breakdown occurred in theassembly 150 or the generator 152 experienced load failure. The maximumpre-delay time 328 is chosen based on the assembly 150 electrical anddesign parameters, such as dielectric breakdown voltages, capacitivestrength, operating voltages, maximum current, etc. and can vary as afunction of the specific assembly 150. The maximum pre-delay time 328institutes a failsafe that can preserve the assembly for further use.

The time between the minimum pre-delay time 322 and the maximumpre-delay time 328 is divided into bins, where each bin corresponds to atime long enough for both the generator 152 and the pulse powercontroller 130 (with their independent clocks) to agree on binidentification, which depends on measurement resolution. Each bincorresponds to a communication or identified modification. In one ormore embodiments, each bin corresponds to bit of data, wherecommunications or identified modifications are transmitted in bits overone or more charge cycles.

In cases where the pulse power controller 130 determines that theelectrodes 144 are discharging successfully into the formation, thepulse power controller 130 determines that charge rate and chargevoltage 312 can be raised to a maximum charge rate and charge voltage inorder to expedite pulse power drilling. In one or more embodiment,charge voltage is constant and a function of assembly 150 parameters. Inother embodiments, charge voltage is adjustable between a minimum chargevoltage and a maximum charge voltage. Based on a determination thatpulse power drilling is proceeding correctly with discharge into theformation, communications corresponding to increase charge rate orincrease charge voltage can be transmitted to the generator 152. In oneor more embodiment, a maximum charge rate and maximum charge voltage canbe determined based on pre-programmed assembly limits, based onalternator 118 output, based on drilling mud flow rate to the turbine116, etc. In response to communications from the pulse power controller130 to increase either charge rate or charge voltage 312, the generator152 can determine that charge rate or charge voltage 312 are currentlyat a maximum and treat communications indicating further increases ascommunications to maintain the maximum charge rate or charge voltage312.

In cases where the electrodes 144 are determined to not be dischargingsuccessfully into the formation, which can be due to off-bottomelectrodes 144 or to electrical malfunctions or reset operations, thecharge rate and charge voltage can be lowered to a minimum charge rateand minimum charge voltage. In one or more embodiments, charge rate isadjusted while charge voltage 312 is constant. The pulse powercontroller 130 can transmit, in response to a determination thatdrilling power is to be ramped down, communications to reduce chargerate or reduce charge voltage 312. In one or more embodiments, a minimumcharge rate or minimum charge voltage can be determined based onpre-programmed assembly limits, based on alternator 118 output, based ondrilling mud flow rate to the turbine 116, etc. In response tocommunications from the pulse power controller 130 to decrease eithercharge rate or charge voltage 312, the generator 152 can determine thatcharge rate or charge voltage 312 are currently at a minimum and treatcommunications indicating further reductions as communications tomaintain the minimum charge rate or charge voltage 312. In one or moreembodiments, the generator 152 can determine that the charge rate orcharge voltage 312 are currently at a minimum and can treatcommunications indicating further reductions in charge rate ascommunications to instead reduce charge voltage and communicationsindicating further reductions in charge voltage as communications toalso reduce charge rate. In one or more embodiments, the generator 152can determine that at least one of the charge rate or charge voltage 312is currently at a minimum and can treat communications indicatingfurther reductions in charge rate or charge voltage 312 ascommunications to reduce charge cycle frequency (which also reducestotal energy emitted by the pulse power electrodes) by increasing thepost-delay time 330, which is the time between the discharge of theelectrodes by the pulse power controller 130 and the beginning of thecharging by the generator 152. In one or more embodiments, the generator152 can determine that at least one of the charge rate or charge voltage312 is currently at a minimum and can treat communications indicatingfurther reductions in charge rate or charge voltage as communications toenter a reset or temporary shutdown mode, which can include increasedpre-delay time, reduced charging rate, reduced charging voltage,alternator 118 slowdown, etc.

Returning to operations of the flowchart 200 of FIG. 2 , from block 208flow continues to block 210. At block 210, a pre-delay time bincorresponding to the communication is selected. The pre-delay time binis selected for communication based on the corresponding modificationdetermined by the operations at block 208. For example, with referenceto the assembly 150 of FIG. 1 , the pulse power controller 130 canselect the pre-delay time bin. For example, the pulse power controller130 can select a time length (which controls timing of the discharge bytriggering one or more switches which cause electrical discharge of thestored voltage for emission from the electrodes 144). The selected timelength will be a time within the bin corresponding to the communicationor modification determined in block 208. In one or more embodiments, apre-delay time is selected based on both the communication ormodification determined in block 208 and on an encoding scheme, shift,or averaging method pre-selected or preprogrammed in both the generator152 and the pulse power controller 130. In some implementations, two ormore consecutive identical communications can be delivered before thegenerator 152 modifies charge cycle parameters, in order to protectagainst transmission or pre-delay time identification errors.Additionally, communications or determined modifications can betransmitted encoded within bits corresponding to pre-delay time bins. Inone or more embodiments, communications or determined modifications,which correspond directly to pre-delay time bins, can be transmitted aswell as additional multi-charge cycle communications or commands byencoding on top of or ordering of the transmitted pre-delay times, suchas using Manchester encoding. From block 210, flow continues to block212.

At block 212, the encoded communication is sent to the generator bydischarging of the capacitors at a time that is within the range of theselected pre-delay time bin. At least one capacitor or pulse powerelectrode is discharged at the selected pre-delay time. For example,with reference to the assembly 150 of FIG. 1 , the pulse powercontroller 130 discharges the capacitors 136 at the selected pre-delaytime 320. To illustrate, the pulse power controller 130 can detect whenthe voltage on the voltage line has reached steady state. Based on theselection of the pre-delay time 320 from block 210, the pulse powercontroller 130 can switch one or more switches to thereby isolate thegenerator 152 from the load and discharging the capacitive charge fromthe capacitors 136 or other electrical elements and through theelectrodes 144 and from there into the formation or drilling fluid. Fromblock 212, flow continues to block 214 at the generator 152.

Flow continues to block 214 from block 206 of the generator 152operations and from block 212 of the pulse power controller 130operations.

At block 214, a corresponding time bin is determined based on thepre-delay time. For example, with reference to the assembly 150 of FIG.1 , the generator 152 makes this determination. In reference to theexample of FIG. 3 , the pre-delay time 320 is measured. The generator152 can then determine which bin includes the pre-delay time 320. Thegenerator 152 can measure the time between when voltage reaches a steadystate and the time of the discharge of voltage by the pulse powercontroller 130. The time length of each bin can be defined as longenough to allow the generator 152 to correctly identify the pre-delaytime 320 and corresponding bin even though the pulse power controller130 and generator 152 run on separate clocks. The time length of a bincan also account for measurement error, including the pulse powercontroller 130 uncertainty in identifying the end of charging portion ofthe charge cycle (which is the beginning of the steady, voltage portionof the charge cycle). From block 214, flow continues to block 216.

At block 216, communication on the voltage line is decoded based on thepre-delay time and the associated bin. For example, with reference tothe assembly 150 of FIG. 1 , the generator 152 decodes the communicationbased on the measured pre-delay time. Modification to the charge rateand charge voltage is determined based on the determined time bin. thecommunication or determined modification encoded by the pulse powercontroller 130 in the bin corresponding to the pre-delay time isidentified by the generator 152. Bins can correspond to anycommunication, as long as the pulse power controller 130 and generator152 agree on bin identity. In one or more embodiments, a first bincorresponding to the minimum pre-delay time 322 plus a time length todecrease errors or uncertainty in detection can correspond to thecommunication or modification used most frequently—such as a maintain orno modification communication. In one or more embodiments, bin timelengths can be unequal. In one or more embodiments, bins can correspondto bits where communications are decoded based on two or more chargecycles. The generator 152 can also determine if the determinedmodification is allowable, based on maximum and minimum charge rates,charge voltages, post-delay times, etc. From block 216, flow continuesto block 218 where the communication is decoded.

At block 218, the charge rate and charge voltage are compared to zero.For example, charge rate or charge voltage is checked to determine ifthe charge rate or charge voltage is zero or below a minimum charge rateor charge voltage. For example, with reference to the assembly 150 ofFIG. 1 , the generator 152 can determine if the charge rate or chargevoltage is zero, or another below a minimum charge rate or chargevoltage. A charge rate or charge voltage of zero or otherwise below theminimum charge rate or charge voltage for drilling corresponds to ashutdown, failsafe, or emergency off procedure. In one or moreembodiment, an infinite post-delay time can also correspond to ashutdown procedure. If the charge voltage or charge rate is zero orbelow a minimum charge rate of charge voltage, the flow can end. If thecharge voltage or charge rate is not zero, i.e. has a value for asubsequent charge cycle, flow can continue to block 202 for anothercharge cycle.

At block 220, the charge rate or charge voltage is modified. Forexample, one or more parameter, i.e. charge rate, charge voltage, etc.,setting is modified or adjusted for the next cycle. For example, withreference to the assembly 150 of FIG. 1 , the generator 152 can modifyor adjust one or more parameter for a subsequent cycle. Block 220indicates the termination of a charge cycle, although charge cyclebeginning and ending can be arbitrary. From block 220, flow continues toblock 202, where another charge cycle begins.

To further illustrate, FIG. 4 depicts a graph of voltage over time foran example four bin communication from pulse power controller togenerator, according to some embodiments. FIG. 4 depicts a graph 400displaying an example plot of voltage (on a y-axis 402) of the voltageline as a function of time (on an x-axis 404). The charging time 310 isthe time during which the generator 152 applies increasing voltage,while the charging rate 314 is the rate of voltage increase during thecharging time 310. The pre-delay time 320 is the time between when thevoltage has reached the charge voltage 312 and the discharge time. Amaximum pre-delay time 432 and a minimum pre-delay time 422 are alsoshown, which bound allowable discharge times. Between the minimumpre-delay time 422 and the maximum pre-delay time 432, four time binsare depicted. A first bin 424, a second bin 426, a third bin 428, and afourth bin 430 can correspond to any assigned communication asprogrammed in the pulse power controller 130 and the generator 152.

In one or more embodiments, the time between the minimum pre-delay time422 and the maximum pre-delay time 432 can be divided into more than twotime bins, such as the four time bins depicted in FIG. 4 . In one ormore embodiments, the first bin 424 corresponds to communicationincreasing the charging rate, the second bin 426 corresponds to acommunication decreasing the charging rate, the third bin 428corresponds to a communication increasing the charge voltage, and thefourth bin 430 corresponds to a communication decreasing the chargevoltage. In one or more embodiments, different bin assignment could beused, such as bits 0, 1, 2, and 3, or bin assignment orders could bedifferent. In one or more embodiments, most commonly used communicationscan be assigned to earlier bins with later bins corresponding to lesscommonly used communications in order to reduce average pre-delay time.A reduced average pre-delay time can increase pulse power electrodedischarge frequency. In one or more embodiments, greater or fewer numberof bins can be used.

FIG. 4 additionally depicts a second cycle after the post-delay time330. For an example pre-delay time corresponding to the third bin 428, asecond cycle with an increased charge voltage 450 is shown. For anexample pre-delay time corresponding to the fourth bin 430, a secondcycle with a decreased charge voltage 460 is shown. The change in chargevoltage can be pre-programmed as a specific value (i.e. a ΔV in volts),as a specific value for an increase and a specific value for a decrease(i.e. ΔV_(increase)≠ΔV_(decrease)), a percentage change (e.g. ΔV isequal to one percent (1%) of the previous charge voltage), a percentagechange for an increase and a percentage change for a decrease (e.g.ΔV_(increase) is 1% of the previous charge voltage and ΔV_(decrease)decrease is 5% of the previous charge voltage), etc. An example voltagechange increase 452 is the difference between charge voltage 312, thecharge voltage of the previous cycle, and increased charge voltage 450.An example voltage change decrease 462 is the difference between chargevoltage 312 of the previous cycle and decreased charge voltage 460. Asthe charge rate is unchanged, an increase or decrease in charge voltagechanges the charging time for a second cycle. In one or more embodiment,the generator 152 can treat a communication to change the charge voltageas a communication to change both the charging rate and the chargevoltage in order to maintain a charging time.

FIG. 5 depicts a flowchart of example operations for voltage linecommunications from a generator to a pulse power controller, accordingto some embodiments. Similar to the operations of the flowchart 200 ofFIG. 2 , operations of a flowchart 500 of FIG. 5 include communicationsthat are also transmitted along the shared voltage line. However,operations of the flowchart 500 include communications going in thedirection opposite of the communications of the flowchart 200 of FIG. 2. The flowchart 500 includes operations described as performed by thegenerator and the pulse power controller for consistency with theearlier description. Such operations can be performed by hardware,firmware, software, or a combination thereof. However, assemblycomponent naming, division, and sub-section organization, and programcode naming, organization, and deployment can vary due to arbitraryoperator choice, assembly ordering, programmer choice, programminglanguage(s), platform, etc. Additionally, operations of flowchart 500are described in reference to the example drilling apparatus 100 of FIG.1 . The flowchart 500 includes the operations of blocks 504, 506, 508,510, and 512 as performed by the generator 152, and the operations ofblock 514, 546, and 518 as performed by the pulse power controller 130.One or more of the operations described as being performed by thegenerator 152 may be instead performed by the alternator 118, acontroller of the generator 152, or a processor of the generator 152.One or more of the operations described as being performed by the pulsepower controller 130 may instead be performed by a processor of thepulse power controller 130 or performed in concert with one or moreswitches of the pulse power controller 130. Additionally, the operationsdepicted as performed by the generator 152 in block 506 can be performedbefore or after the operations of block 508, 510, and 512.

FIG. 5 depicts a flowchart of example operations for voltage linecommunications from the generator 152 to the pulse power controller 130,according to some embodiments. The generator 152 can control a voltagecharging cycle, while the pulse power controller 130 can control thevoltage discharge. By modifying various parts of the charge anddischarge cycle, communication between the generator 152 and pulse powercontroller 130 can be enabled over the voltage connection while theelectrodes 144 can continue to drill via electrical discharging.

At block 502, a charge cycle is initiated. For example, with referenceto the assembly 150 of FIG. 1 , a charge cycle can be initiated for boththe generator 152 and the pulse power controller 130. The start of thecharging cycle can be measured from the discharge of the previous cycle.A post-delay time (which will be discussed in reference to FIG. 6 ),between when the generator 152 detects the discharge of the previouscycle and when the generator 152 begins charging of the voltage line forthe current cycle, can be measured by both the generator 152 and thepulse power controller 130. As previously discussed in reference to FIG.2 , the generator 152 and the pulse power controller 130 can haveindependent clocks, in which case there can be disagreement on the exactbeginning of each cycle between the generator 152 and the pulse powercontroller 130. In order to reduce errors and simplify communication,time bins can be used to account for discrepancy in measurement or clocktimes when communicating between the generator 152 and the pulse powercontroller 130. Block 502 begins a loop for each charge cycle thatcontinues for the generator 152 at block 504. In one or moreembodiments, flow from block 502 can also optionally continue to block514 of the pulse power controller 130. Alternatively, the start of eachcycle can be detected by the pulse power controller 130 when thegenerator 152 begins charging of the voltage line. Such an example isdescribed in reference to a flow of operations from block 512 to 514 aswill be discussed later.

To illustrate, FIG. 6 depicts a graph of voltage over time for anexample communication from the generator to the pulse power controller,according to some embodiments. FIG. 6 depicts a graph 600 displaying anexample plot of voltage (on a y-axis 602) of the voltage line as afunction of time (on an x-axis 604). The graph 600 of FIG. 6 isdescribed in reference to the example drilling apparatus 100 of FIG. 1 .The charging time 310 is when the generator 152 applies increasingvoltage on the voltage line connecting the generator 152 and the pulsepower controller 130. The charging rate 314 is the slope of the voltagecurve during the charging time 310 to the charge voltage 312. A minimumpre-delay time 622 and a maximum pre-delay time 632 are shown, alongwith a discharge time 670 when the pulse power controller 130 dischargesthe voltage through the electrodes 144. A pre-delay time 620 correspondsto the measured time difference between the discharge time 670 and theend of the charging time 310. A minimum post-delay time 672 and amaximum post-delay time 674 are also shown. A post-delay time 640corresponds to the measured time difference between the discharge time670 and the beginning of the second cycle at time 680. The time periodbetween the minimum post-delay time 672 and the maximum post-delay time674 is divided into bins such that the post-delay time 640 correspondsto a single bin. Bins can vary in length. The maximum post-delay time674 can correspond to a shut down time or a communication initiating acorrective or diagnostic window.

Returning to FIG. 5 at block 504, the communication to be transmitted onthe shared voltage line to the pulse power controller is determined.Optionally, the charge cycle parameters, which can include the chargerate, the charge voltage 312 and the post-delay time 640, are determinedfor the current charge cycle based on modifications from a previouscycle or pre-programmed values. For example, with reference to theassembly 150 of FIG. 1 , the generator 152 can determine parameters forthe current charge cycle. The charge rate and charge voltage 312 can beiteratively adjusted by communication between the pulse power controller130 and the generator 152 for each charge cycle, as described inreference to FIGS. 2-4 . For a first charge cycle or any charge cyclefor which the generator 152 does not have previous cycle data, thecharge cycle parameters can be pre-programmed or set to baseline,minimum, or maximum values. In one or more embodiment, the post-delaytime 640 can be adjusted by the generator 152 to fall into a time binthat correspond to pre-determined communications or requests formodifications from the generator 152 to the pulse power controller 130.In one or more embodiments, the post-delay time 640 can be adjusted bythe generator 152 in response to a communication or requestedmodification sent from the pulse power controller 130 to the generator152. For example, the post-delay time 640 can be extended in response toa pulse power controller request to reduce the charging rate or reducethe charge voltage when the charging rate and charge voltage are atminimum values. Flow continues from block 504 to block 506.

At block 506, a post-delay time is selected corresponding to thecommunication to be transmitted to the pulse power controller. Forexample, with reference to the assembly 150 of FIG. 1 , the generator152 can select the post-delay time 640. For example, the generator 152can determine that the generator 152 (or associated components), thepulse power controller 130, or one or more switches of the pulse powercontroller 130 is malfunctioning or otherwise is to be reset.Accordingly, the generator 152 can select a post-delay time thatcorresponds to a reset command. In another example, if a change in theelectrode 144 location, alternator 118 operation, flow of drilling mudor other signal is detected, the generator can communicate that powercan be ramped up or ramped down or any other pre-programmedcommunication to the pulse power controller 130. In one or moreembodiments, the generator 152 can select a post-delay time thatcorresponds to a command to the pulse power controller 130 to initiateshutdown—either controlled or emergency.

As described in reference to FIG. 6 , the generator 152 can communicateto the pulse power controller 130 via a selecting a post-delay time 640between the discharge of the previous cycle and the start of thecharging time 310 of the current cycle. Any communication can betransmitted by the generator 152 to the pulse power controller 130 basedon pre-programmed correlations between bins or ranges of post-delaytimes 640 and defined communications. In one or more embodiments,post-delay time bins can be pre-assigned to two or more bits (such as 0and 1) and any communication can be transmitted by the generator 152 tothe pulse power controller 130 by encoding over one or more cycles. Inone or more embodiments, time bins can be unequal lengths. Additionally,if a maximum post-delay time 674 is reached before the generator 152begins a charging cycle, the pulse power controller 130 can treat thatas a communication that drilling is stopped or paused. In someimplementations, a communication can be sent to the pulse powercontroller 130 so that the pulse power controller 130 and the generator152 can coordinate on a subsequent cycle. For example, the post-delaytime 640 can be selected that corresponds to a communication thatdrilling has ended. In this case, the pulse power controller 130receives a communication that the current cycle is the final cycle—butdrilling is not stopped until the subsequent cycle when the post-delaytime 640 is infinite. In one or more embodiments, communications can beassigned to one or more bins where the first bin is assigned to the mostexpected communication and the last bin is assigned to a communicationthat is least common in order to expedite the drilling rate. Flowcontinues from block 506 to block 508, although block 506 can optionallybe performed instead after block 510.

At block 508, the parameters for the current cycle are compared tolimits in order to determine if they exceed limits or indicate reset.For example, with reference to the assembly 150 of FIG. 1 , thegenerator 152 can determine if any parameters exceed limits or indicatereset or shutdown procedures. For example, the charging rate, the chargevoltage 312, and the charging time 310 can be compared to both maximumand minimum limits. If parameters exceed limits or indicate a reset isto be performed, flow continues to block 510. If parameters do notexceed limits, flow continues to block 512. In one or more embodiments,the post-delay time 640 can be increased in response to a minimumcharging rate, minimum charge voltage, or maximum charging time. In oneor more embodiments, the post-delay time 640 can be decreased inresponse to a maximum charging rate, maximum charge voltage, or minimumcharging time.

Current and voltage discharged by the pulse power controller 130 to theelectrodes 144 can be measured. Current draw or power load can bedetected outside of a pre-selected range or change in current and powerdischarged to the electrodes detected between a previous cycle and acurrent cycle. In those cases, high or low current or high or low powerdischarges can correspond to malfunctioning of the electrodes 144, oneor more switches, or disruption of the assembly in the wellbore. In oneor more embodiments, a reset procedure can be performed by either thegenerator 152 or the pulse power controller 130 of one or moresub-assemblies. In some implementations, the generator 152 can transmita communication to the pulse power controller 130 after discharge (oroptionally, during a long post-delay time period) to reset or toggleswitches, clear caches, or other resetting operations.

At block 510, additional post-delay time is selected to perform acorrective action or diagnostic routine. For example, with reference tothe assembly 150 of FIG. 1 , the generator 152 can select an additionalpost-delay time based on the determination that corrective action is tobe performed or that a diagnostic routine is selected. A diagnosticroutine can comprise one or more long post-delay times consistent with adiagnostic window in during which electrical discharges are paused. Inone or more embodiments, a time window for corrective or diagnosticaction can correlate to a longest post-delay time bin, shorter than themaximum post-delay time 674 indicating shutdown. Alternatively, acommunication correlating to initiation of corrective or diagnosticaction can be sent in a cycle while the corrective action or diagnosticroutine is initiated during the post-delay time 640 in a subsequentcycle. In one or more embodiments, the assembly 150 can enter acorrective action or diagnostic routine in which several long post-delaytimes alternate with minimal charging rate or minimal charge voltage andpulse power electrode discharge cycles. In one or more embodiments, acorrective action or diagnostic routine can end based on communicationfrom the pulse power controller 130 (e.g. communication via thepre-delay time 620). From block 510 flow continues to block 512.

At block 512, the voltage line is charged at the charge rate to thecharge voltage after the selected post-delay time. For example, thevoltage line charging can be after the post-delay time 640 has passedafter the previous cycle (i.e. the capacitive or other discharge via theelectrodes 144). For example, with reference to the assembly 150 of FIG.1 the generator 152 can apply voltage to the shared voltage line.Because the discharge to the electrodes 144 is a sharp impulse in thevoltage curve, the discharge time 670 can be detected with reasonablecertainty. The generator 152 controls the time at which charging begins,and therefore can measure the post-delay time 640. From block 512, flowcontinues to block 514 at the pulse power controller 130.

At block 514, the time bin corresponding to the post-delay time isdetermined. The post-delay time 640 between the pulse power electrodedischarge and when the charging of the voltage line is detected ismeasured. For example, with reference to the assembly 150 of FIG. 1 ,the pulse power controller 130 measure the post-delay time 640 andidentify to which bin it corresponds. Because the pulse power controller130 controls the discharge but must detect the beginning of the chargingcycle initiated by the generator 152, the pulse power controller 130experiences uncertainty in measurement. Post-delay time bin sizes allowthe pulse power controller 130 to read communications with greaterconfidence. For long bin times, such as those associated with acorrective or diagnostic window or those initiating shutdown, the pulsepower controller 130 can determine that the post-delay time is longerthan a maximum post-delay time 674 and begin reset or shutdownprocedures without detecting a charging rate or charge voltage on thevoltage line or from the generator 152. From block 514 flow continues toblock 516.

At block 516, based on the determined time bin of the post-delay time,the communication is determined. For example, with reference to theassembly 150 of FIG. 1 , the pulse power controller 130 can determinewhich communication has been sent. The pulse power controller 130 candetermine the identity of the communication that can be sent from thegenerator 152, alternator 118, or other sub-assembly component. Acommunication can include a request for modification of the pulse powercontroller 130 operation, information about the drilling mud flow rate,a communication indication shutdown, etc. In cases where the pulse powercontroller 130 and the generator 152 are autonomous once deployed in thewellbore, one or more pre-programmed communications, including multi-bitcommunications, can be transmitted including answers to communicationsor queries sent from the pulse power controller 130 to the generator152. In one or more embodiments, communications can be sent to the pulsepower controller 130 that were received from one or more tool above thealternator 118 or outside the assembly 150. From block 516 flowcontinues to optional block 518.

At block 518, optionally, a corrective action or diagnostic routine isperformed based on the determined communication of the time bincorresponding to the post-delay time 640. Any communication received inthe current charge cycle, or upon any multi-cycle communicationspreviously received and not yet completed are operated upon. Forexample, with reference to the assembly 150 of FIG. 1 , the pulse powercontroller 130 can reset operate upon the received communication. In oneor more embodiments, this can include resetting one or more switches ofthe switch bank 138. If the switches are malfunctioning or mistimed, thealternator 118 and the generator 152 may not be protected from the powerload while the electrodes 144 discharge. If the switches are notdischarging correctly, such as slowly rather than substantiallyinstantaneously (i.e. less than 1 ms) or other faults are occurring, theswitches can be reset. In one or more embodiments, the pulse powersection 154 may enter a diagnostic sequence, either independently or inconcert with the generator 152, in order to determine if the switches,the wellbore, a short or electrical failure, etc. is causing out ofrange electrical or power draw during pulse power drilling. Onecommunication or post-delay time bin may correspond to a diagnosticsequence and a reset, or the generator 152 can request these actionsseparately using different post-delay time bins. The pulse powercontroller 130 can also performs its primary function (i.e.discharging), while interpreting and implementing any communicationsfrom the generator 152. If the generator 152 is charging the voltageline, the pulse power controller 130 discharges the pulse powerelectrodes at the maximum pre-delay time 632, in order to protect theassembly 150. If the generator 152 does not charge the voltage line, thepulse power controller 130 can assume that shut down—either temporary orpermanent—has been initiated. From block 518 flow continues to block520.

At block 520, it is determined if the communication indicates a shutdownprocedure. If a shutdown procedure has been initiated, the assembly 150(i.e. both the pulse power controller 130 and the generator 152) candetermine a shutdown is required. For example, with reference to theassembly 150 of FIG. 1 , the pulse power controller 130, generator 152,alternator 118, etc. or any other part of the assembly 150 can determinethat as shutdown is initiated, has occurred, or is occurring. If ashutdown has not been initiated, drilling continues and the pulse powercontroller 130 discharges the electrodes 144 and flow continues to thenext charge cycle at block 502. If a shutdown has been initiated, aswitch to the generator 152 can be closed or switches to both thegenerator 152 and the drilling fluid can be opened in order to groundthe assembly 150 and prevent erroneous capacitive charging. If shutdownis initiated, the flow terminates once the generator 152 and pulse powercontroller 130 determine that no more cycles are currently occurring.

Alternatively or in addition to the example operations for voltage linecommunications described in reference to FIGS. 2 and 5 , there can bevoltage line communications using additive signals. To illustrate, FIG.7 depicts a flowchart of example operations for voltage linecommunications between a pulse power controller and a generator usingadditive signals during pre-delay and post-delay time periods, accordingto some embodiments. A flowchart 700 of FIG. 7 includes operationsdescribed as performed by the generator and the pulse power controllerfor consistency with the earlier description. Such operations can beperformed by hardware, firmware, software, or a combination thereof.However, assembly component naming, division, and sub-sectionorganization, and program code naming, organization, and deployment canvary due to arbitrary operator choice, assembly ordering, programmerchoice, programming language(s), platform, etc. Additionally, operationsof the flowchart 700 are described in reference to the example drillingapparatus of FIG. 1 . The flowchart 700 includes the operations ofblocks 708, 710, 712, and 714 as performed by the generator 152, and theoperations of block 704, 706, 716, and 718 as performed by the pulsepower controller 130. One or more of the operations described as beingperformed by the generator 152 may be instead performed by thealternator 118, a controller of the generator 152, or a processor of thegenerator 152. One or more of the operations described as beingperformed by the pulse power controller 130 may instead be performed bya processor of the pulse power controller 130, or performed in concertwith one or more switches of the pulse power controller 130.

FIG. 7 includes operations related to communication between componentsof the assembly 150 via the voltage line that transfers voltage andcurrent over a field joint (or any other type of joint or junction).While the generator 152 controls the voltage charging cycle, the pulsepower controller 130 controls the voltage discharge. By adding signalsto various parts of the charge and discharge cycle, the generator 152and pulse power controller 130 can communicate data over the voltageconnection while also continuing to drill with the electrodes 144.

At block 702, a charge cycle is initiated. For example, with referenceto the assembly 150 of FIG. 1 , a charge cycle can be initiated for thegenerator 152 and the pulse power controller 130. The generator 152 andthe pulse power controller 130 can have independent clocks or clocksthat are synched to one or more events of the charge cycle. Therefore,the start of the charge cycle—which is based on the end of the previouscharge cycle or the beginning of charging of the voltage line—can bemeasured as beginning at different times in the generator 152 and thepulse power controller 130. For a first charge cycle or a charge cyclefor which previous cycle data is not available, the charge cyclebeginning can be determined by the generator 152, which initiates afirst charging of the voltage line based on electrical charging via thealternator 118 by the turbine 116 which is controlled by drilling mudflow. A time difference between the beginning of a given charge cycle asmeasured by the generator 152 and the pulse power controller 130 is aresult of separate clocks and can further be confounded by measurementaccuracy. Block 702 begins a loop for each charge cycle that continuesfor the pulse power controller 130 at block 704 and starts at thegenerator 152 when flow reaches block 708. The beginning of the chargecycle is arbitrary and can be measured from the discharge time, from thebeginning of the charging time, etc. as long as the pulse powercontroller 130 and the generator 152 recognize the same staring event.

At block 704, communication for the generator is encoded. A message orcommunication is encoded in an analog or digital signal at the pulsepower controller 130. For example, with reference to the assembly 150 ofFIG. 1 , the pulse power controller 130 can select and encode thecommunication. The communication can be encoded using any suitableencoding scheme, including frequency modulation, amplitude modulation,Manchester shift, etc. The communication can be one or more bits inlength. The communication can correspond to a command, request, orpre-selected set of communications agreed upon by the pulse powercontroller 130 and the generator 152. The set of communications that canbe sent from the pulse power controller 130 to the generator 152 may bethe same or different from the set of communications that can be sentfrom the generator 152 to the pulse power controller 130. Thecommunication can also contain data about one or more drilling parameterto be transferred between components of the assembly 150 or to be storedas data in a component of the assembly 150. The communication caninclude any communication previously described in reference to FIGS. 2and 5 .

To illustrate, FIG. 8 depicts a graph of voltage over time for anexample communication in which a communication signal is embedded withinthe DC signal during the pre-delay or post-delay, according to someembodiments. FIG. 8 depicts a graph 800 displaying an example plot ofvoltage (on a y-axis 802) of the voltage line as a function of time (onan x-axis 804). Operations of FIG. 8 are described in reference to theexample drilling apparatus 100 of FIG. 1 . The charging time 310 is whenthe generator 152 applies increasing voltage on the voltage lineconnecting the generator 152 and the pulse power controller 130, whilethe charging rate 314 is the slope of the voltage curve during thecharging time 310 to the charge voltage 312. A minimum pre-delay time822 and a maximum pre-delay time 828 are shown, along with a dischargetime 870 when the pulse power controller 130 discharges the voltagethrough the electrodes 144. A pre-delay time 820 corresponds to themeasured time difference between the discharge time 870 and the end ofthe charging time 310. A minimum post-delay time 872 and a maximumpost-delay time 874 are also shown. A post-delay time 840 corresponds tothe measured time difference between the discharge time 870 and thebeginning of the second cycle at time 844.

During each of the portions of the charging cycle for which voltage isconstant (i.e. for the pre-delay time 820 and the post-delay time 840),an information signal can be added to or transmitted on top of thevoltage. In FIG. 8 , voltage is not shown to scale so that theinformation signal can be identified at both the highest voltage of thecycle (which can be approximately 16 kV) and at the lowest voltage ofthe cycle (which can be approximately 0 V). For the first cycle, ananalog signal 850 is shown during the pre-delay time 820. The analogsignal is shown as beginning after the minimum pre-delay time 822, wherean offset from the end of the charging time 310 prevents the beginningof the analog signal 850 from being overwritten by the change in voltageduring the charging time 310. An analog signal 860 is shown during thepost-delay time 840. The analog signal 860 is shown as beginning at thedischarge time 870, but can also begin after a minimum post-delaydetection time (where the minimum post-delay time detection time may ormay not be the same as the minimum post-delay time 872). For a secondcycle, an analog signal 852 is also shown during the pre-delay time. Insome embodiments, the added signals can be analog or digital or acombination thereof. Frequency, time, and voltage are not shown toscale.

Returning to FIG. 7 at block 706, the encoded communication is added tothe voltage line during the pre-delay. The encoded message orcommunication can be added to the signal (as an information signal) onthe voltage line during the pre-delay time 820. For example, withreference to the assembly 150 of FIG. 1 , the pulse power controller 130can add the encoded communication to the voltage line signal. During thepre-delay time 820 voltage is at a maximum or otherwise elevated level.Adding an information signal, such as analog signal 850, to a voltagewhich can be approximately 16 kV can require complex electronics. In oneor more embodiments, an information signal can be combined with thecharge voltage though multiplexing or other electronic combination. Inone or more embodiments, an information signal can be embedded in thecharge voltage 312. In one or more embodiments, an information signalcan be directly encoded in the charge voltage 312 or encoded in thecurrent drawn at the charge voltage 312. Any appropriate method foradding the information signal to the pre-delay time 820 can be used.

At block 708, the encoded communication in the pre-delay from the pulsepower controller 130 is read. The encoded message or communication isdetected and read during the pre-delay time 820. For example, withreference to the assembly 150 of FIG. 1 , the generator 152 can read theencoded communication. The information is read from oscillations in thecharge voltage 312 during the pre-delay time 820. The generator 152 candetermine when the charge voltage 312 is reached, and therefore it cancontain circuitry that can measure changes in the charge voltage 312 orabsolute value of the charge voltage 312.

At block 710, the communication encoded in the pre-delay is decoded. Thecommunication or information can be decoded or extracted from theinformation signal. For example, with reference to the assembly 150 ofFIG. 1 , the generator 152 can decode the communication. Thecommunication or information can then be stored or acted upon, based onthe communication or information that has been decoded and thepre-programmed responses of the generator 152 to such data. In one ormore embodiment, a communication from the pulse power controller 130 canbe stored as data by the generator 152 or forwarded to one or moresub-components of the generator 152 or transmitted to components of theassembly 150 above the generator 152, such as the alternator 188, theturbine 116, the logging tools 148, etc. In one or more embodiment, thecommunication can cause the generator 152 to alter one or more chargeparameter for a subsequent cycle, as described in reference to FIG. 2 .

At block 712, a communication for the pulse power controller is encoded.A message or communication is encoded in an analog or digital signal atthe generator 152. For example, with reference to the assembly 150 ofFIG. 1 , the generator 152 can select and encode the communication to besent to the pulse power controller 130. The communication can be encodedusing any suitable encoding scheme, including frequency modulation,amplitude modulation, Manchester shift, etc. The communication can beone or more bits in length. The method of encoding at the generator 152may be different that the communication of encoding used at the pulsepower controller 130. The communication can correspond to a command,request, or pre-selected set of communications agreed upon by the pulsepower controller 130 and the generator 152. The communication can alsocontain data about one or more power parameter to be transferred betweencomponents of the assembly 150 or to be stored as data in the pulsepower controller 130. The communication can include any communicationpreviously described in reference to FIGS. 2 and 5 .

At block 714, the encoded communication is added to the voltage lineduring the post-delay. The encoded message or communication can be addedto the signal on the voltage line (as an information signal) during thepost-delay time 840. For example, with reference to the assembly 150 ofFIG. 1 , the generator 152 can add the encoded communication to thevoltage line signal. During the post-delay time 840 voltage is at aminimum or approximately zero. Adding an information signal, such asanalog signal 860, can require complex or standard electronics. In oneor more embodiments, an information signal added multiplexing or otherelectronic combination. Any appropriate method for adding theinformation signal to the post-delay time 840 can be used.

At block 716, the encoded communication from the generator is readduring the post-delay. The encoded communication or message is detectedand read during the post-delay time 840. For example, with reference tothe assembly 150 of FIG. 1 , the pulse power controller 130 can read thedetected encoded communication. The information is read fromoscillations in the voltage or current during the post-delay time 840.The pulse power controller 130 can contain circuitry that can measurechanges in the voltage or absolute value of the charge voltage, whichcan detect the encoded communication or information signal as well asdetect the end of the charging time 310.

At block 718, the communication is decoded from the post-delay. Themessage or communication can be decoded or extracted from theinformation signal. For example, with reference to the assembly 150 ofFIG. 1 , the pulse power controller 130 can decode the communicationfrom the post-delay time 840. The communication or information can thenbe stored or acted upon, based on the communication or information thathas been decoded and the pre-programmed responses of the pulse powercontroller 130 to such data. In one or more embodiment, a communicationfrom the generator 152 can be stored as data by the pulse powercontroller 130. In one or more embodiment, the communication can causethe pulse power controller 130 to alter one or more charge parameter fora subsequent cycle or setting for one or more capacitors or switches, asdescribed in reference to FIG. 2 .

At block 720, the determination is made if there is to be an additionalcharge cycle. For example, with reference to the assembly 150 of FIG. 1, the generator 152 or the pulse power controller 130 can determine ifan additional charge cycle is warranted. If the communication decoded atthe generator 152 in block 710 is a command for shutdown, eitheremergency or standard procedure, then no additional charge cycle isrequested. In one or more embodiments, the pulse power controller 130can request a shut down in a communication sent to the generator 152 ora shutdown procedure can require two or more charge cycles. If thecommunication decoded at the pulse power controller 130 at block 718initiates a shutdown, one or more charge cycles may also be required. Ifadditional charge cycles are required or requested flow can continues toblock 702 for another charge cycle. If no additional charge cycles arerequested, the flow ends.

FIGS. 2, 5, and 7 are annotated with a series of numbers. These numbersrepresent stages of operations. Although these stages are ordered forthis example, the stages illustrate one example to aid in understandingthis disclosure and should not be used to limit the claims. Subjectmatter falling within the scope of the claims can vary with respect tothe order and some of the operations.

The flowcharts are provided to aid in understanding the illustrationsand are not to be used to limit scope of the claims. The flowchartsdepict example operations that can vary within the scope of the claims.Additional operations may be performed; fewer operations may beperformed; the operations may be performed in parallel; and theoperations may be performed in a different order. For example, theoperations depicted in blocks 506 and 510 can be performed in parallelor concurrently. With respect to FIG. 5 , an additional post-delay timeis not necessary. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented byprogram code. The program code may be provided to a processor of ageneral-purpose computer, special purpose computer, or otherprogrammable machine or apparatus.

As will be appreciated, aspects of the disclosure may be embodied as asystem, method or program code/instructions stored in one or moremachine-readable media. Accordingly, aspects may take the form ofhardware, software (including firmware, resident software, micro-code,etc.), or a combination of software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”The functionality presented as individual modules/units in the exampleillustrations can be organized differently in accordance with any one ofplatform (operating system and/or hardware), application ecosystem,interfaces, programmer preferences, programming language, administratorpreferences, etc.

Any combination of one or more machine readable medium(s) may beutilized. The machine-readable medium may be a machine-readable signalmedium or a machine-readable storage medium. A machine readable storagemedium may be, for example, but not limited to, a system, apparatus, ordevice, that employs any one of or combination of electronic, magnetic,optical, electromagnetic, infrared, or semiconductor technology to storeprogram code. More specific examples (a non-exhaustive list) of themachine readable storage medium would include the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a portable compact disc read-only memory (CD-ROM), anoptical storage device, a magnetic storage device, or any suitablecombination of the foregoing. In the context of this document, amachine-readable storage medium may be any tangible medium that cancontain, or store a program for use by or in connection with aninstruction execution system, apparatus, or device. A machine-readablestorage medium is not a machine-readable signal medium.

A machine-readable signal medium may include a propagated data signalwith machine readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Amachine readable signal medium may be any machine readable medium thatis not a machine readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a machine-readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

The program code/instructions may also be stored in a machine readablemedium that can direct a machine to function in a particular manner,such that the instructions stored in the machine readable medium producean article of manufacture including instructions which implement thefunction/act specified in the flowchart and/or block diagram block orblocks.

Example Computer

FIG. 9 depicts an example computer, according to some embodiments. Acomputer 900 of FIG. 9 can be representative of a computer or controllerin the generator 152 or the pulse power section 154 of FIG. 1 . Thecomputer 900 of FIG. 9 can also be representative of a computer orcontroller of the pulse power controller 130, which is included in thepulse power section 154.

FIG. 9 depicts an example computer with a controller. The computer 900includes a processor 901 (possibly including multiple processors,multiple cores, multiple nodes, and/or implementing multi-threading,etc.). The computer 900 includes a memory 907. The memory 907 may besystem memory or any one or more of the above already described possiblerealizations of machine-readable media. The computer 900 also includes abus 903 and a network interface 905. The computer 900 also includes acontroller 911. The controller 911 may be the controller of either thegenerator 152 or the pulse power controller 130. Any one of thepreviously described functionalities may be partially (or entirely)implemented in hardware and/or on the processor 901. For example, thefunctionality may be implemented with an application specific integratedcircuit, in logic implemented in the processor 901, in a co-processor ona peripheral device or card, etc. Further, realizations may includefewer or additional components not illustrated in FIG. 9 (e.g., videocards, audio cards, additional network interfaces, peripheral devices,etc.). The processor 901 and the network interface 905 are coupled tothe bus 903. Although illustrated as being coupled to the bus 903, thememory 907 may be coupled to the processor 901.

While the aspects of the disclosure are described with reference tovarious implementations and exploitations, it will be understood thatthese aspects are illustrative and that the scope of the claims is notlimited to them. In general, techniques for voltage line communicationas described herein may be implemented with facilities consistent withany hardware system or hardware systems. Many variations, modifications,additions, and improvements are possible.

Plural instances may be provided for components, operations orstructures described herein as a single instance. Finally, boundariesbetween various components, operations and data stores are somewhatarbitrary, and particular operations are illustrated in the context ofspecific illustrative configurations. Other allocations of functionalityare envisioned and may fall within the scope of the disclosure. Ingeneral, structures and functionality presented as separate componentsin the example configurations may be implemented as a combined structureor component. Similarly, structures and functionality presented as asingle component may be implemented as separate components. These andother variations, modifications, additions, and improvements may fallwithin the scope of the disclosure.

Example Embodiments

As used herein, the term “or” is inclusive unless otherwise explicitlynoted. Thus, the phrase “at least one of A, B, or C” is satisfied by anyelement from the set {A, B, C} or any combination thereof, includingmultiples of any element.

The invention claimed is:
 1. A method comprising: periodicallyperforming a process of emitting an electrical discharge into asubsurface formation from a drilling assembly positioned in a boreholeformed in the subsurface formation, wherein the process comprises,charging, by a generator of the drilling assembly for a first chargecycle, a capacitive element of the drilling assembly based onapplication of a voltage to a voltage line; detecting, by a pulse powercontroller of the drilling assembly, a drop in the voltage on thevoltage line that is in response to emitting the electrical dischargefrom the capacitive element; transmitting, by the pulse powercontroller, a communication via the voltage line after a time delay;decoding, by the generator, the communication based on the time delay;and modifying, by the generator, a parameter of the process based on thedecoded communication.
 2. The method of claim 1, wherein the process ofemitting the electrical discharge into the subsurface formationcomprises pulse power drilling.
 3. The method of claim 1, whereindecoding the communication comprises: determining, after a level of thevoltage to the voltage line has exceeded a full charge threshold, apre-delay time that is a time between after the level of the voltage hasexceeded the full charge threshold and before the drop in the level ofthe voltage on the voltage line that is in response to emitting theelectrical discharge; and decoding the communication based on a value ofthe pre-delay time.
 4. The method of claim 3, wherein modifying theparameter comprises: adjusting the parameter by a first value based onthe value of the pre-delay time being in a first range; and adjustingthe parameter by a second value based on the value of the pre-delay timebeing in a second range.
 5. The method of claim 1, wherein modifying theparameter comprises modifying at least one of a charge rate, a chargingtime, a level of the voltage, a pre-delay time that is a time betweenafter the level of the voltage has exceeded a full charge threshold andbefore the drop in the level of the voltage on the voltage line that isin response to emitting the electrical discharge, and a post-delay timethat is a time between after the drop in the level of the voltage on thevoltage line that is in response to emitting the electrical dischargeand a start of a next charge cycle.
 6. The method of claim 1, whereindecoding the communication comprises: determining a post-delay time thatis a time between after the drop in a level of the voltage on thevoltage line that is in response to emitting the electrical dischargeand a start of a next charge cycle; and decoding the communication basedon a value of the post-delay time.
 7. The method of claim 1, whereindecoding the communication comprises: detecting a parameter of at leastone of the voltage and a current of the voltage line that comprises atleast one of an amplitude and a frequency; and decoding thecommunication based on a value of the parameter.
 8. The method of claim1, wherein decoding the communication comprises: detecting an encodedsignal added to the voltage that comprises at least one of an analogsignal and a digital signal; and decoding the communication based on theencoded signal.
 9. The method of claim 1, wherein modifying theparameter comprises modifying the parameter based on the communicationand at least one more communication encoded in the voltage in at leastone more charge cycle.
 10. The method of claim 1, wherein the process ofemitting the electrical discharge comprises: charging, by the generatorfor a second charge cycle based on the modified parameter, thecapacitive element based on the application of the voltage to thevoltage line.
 11. The method of claim 2, wherein the pulse powerdrilling comprises: in response to determining that a drill bit of thedrilling assembly is not in contact with a bottom of the borehole,encoding a subsequent communication in a subsequent charge cycle in thevoltage on the voltage line, wherein the subsequent communicationincludes a command to reduce at least one of a charge rate of chargingthe capacitive element and a level of the voltage.
 12. The method ofclaim 1, wherein the periodically process of emitting the electricaldischarge comprises: encoding, by the pulse power controller, thecommunication in the voltage on the voltage line by varying at least oneof, a pre-delay time that is a time between after a level of the voltagehas exceeded a full charge threshold and before the drop in the level ofthe voltage on the voltage line that is in response to emitting theelectrical discharge, an encoded signal added to the voltage thatcomprises at least one of an analog signal and a digital signal, andwherein the decoding of the communication comprises decoding of thecommunication by the generator.
 13. The method of claim 12, wherein theprocess of emitting the electrical discharge comprises: encoding, by thegenerator, a different communication in the voltage on the voltage lineby varying at least one of, a post-delay time that is a time betweenafter the drop in the level of the voltage on the voltage line that isin response to emitting the electrical discharge and a start of a nextcharge cycle, a charge rate, a charging time, the level of the voltage,and an encoded signal added to the voltage that comprises at least oneof an analog signal and a digital signal; and decoding, by the pulsepower controller, the different communication in the voltage on thevoltage line.
 14. A system comprising: a pulse power drilling assemblyconfigured to pulse power drill a borehole formed in a subsurfaceformation, wherein the pulse power drill assembly comprises, acapacitive element; a generator electrically coupled to the capacitiveelement through a voltage line, wherein the generator is to generate avoltage that is to be transmitted through the voltage line to charge thecapacitive element for a first charge cycle; a drill bit having anelectrode that is electrically coupled with the capacitive element; apulse power controller to control the electrode to perform a process toemit of an electrical discharge from the electrode into the subsurfaceformation to pulse power drill the borehole; a processor; and acomputer-readable medium having instructions stored thereon that areexecutable by the processor to cause the processor to, detect, by thepulse power controller, a drop in the voltage on the voltage line thatis in response to emission of the electrical discharge; transmit, by thepulse power controller, a communication via the voltage line after atime delay; decode, by the generator, the communication based on thetime delay; and modify, by the generator, a parameter of pulse powerdrilling of the borehole based on the decoded communication.
 15. Thesystem of claim 14, wherein the instructions that are executable by theprocessor to cause the processor to decode the communication compriseinstructions that are executable by the processor to cause the processorto: determine, after a level of the voltage to the voltage line hasexceeded a full charge threshold, a pre-delay time that is a timebetween after the level of the voltage has exceeded the full chargethreshold and before the drop in the level of the voltage on the voltageline that is in response to the emission of the electrical discharge;and decode the communication based on a value of the pre-delay time. 16.The system of claim 15, wherein the instructions that are executable bythe processor to cause the processor to modify the parameter compriseinstructions that are executable by the processor to cause the processorto: adjust the parameter by a first value based on the value of thepre-delay time being in a first range; and adjust the parameter by asecond value based on the value of the pre-delay time being in a secondrange.
 17. The system of claim 14, wherein the instructions that areexecutable by the processor to cause the processor to modify theparameter comprise instructions that are executable by the processor tocause the processor to modify at least one of a charge rate, a chargingtime, a level of the voltage, a pre-delay time that is a time betweenafter the level of the voltage has exceeded a full charge threshold andbefore the drop in the level of the voltage on the voltage line that isin response to the emission of the electrical discharge, and apost-delay time that is a time between after the drop in the level ofthe voltage on the voltage line that is in response to the emission ofthe electrical discharge and a start of a next charge cycle.
 18. Anon-transitory, computer-readable medium having instructions storedthereon that are executable by a computing device to: monitor a voltageon a voltage line that is electrically coupled to a generator of adrilling assembly and a capacitive element of the drilling assembly,wherein the generator is to charge the capacitive element based onapplication of the voltage to the voltage line, wherein the drillingassembly is to perform pulse power drilling of a borehole into asubsurface formation by a process to emit an electrical discharge intothe subsurface formation based on power stored in the capacitiveelement; detect, by a pulse power controller of the drilling assembly, adrop in the voltage on the voltage line that is in response to anemission of the electrical discharge; transmit, by the pulse powercontroller, a communication via the voltage line after a time delay;decode, by the generator, the communication based on the time delay; andmodify, by the generator, a parameter of the pulse power drilling basedon the decoded communication.
 19. The non-transitory, computer-readablemedium of claim 18, wherein the instructions to decode the communicationcomprise instructions to: determine, after a level of the voltage to thevoltage line has exceeded a full charge threshold, a pre-delay time thatis a time between after the level of the voltage has exceeded the fullcharge threshold and before the drop in the level of the voltage on thevoltage line that is in response to the emission of the electricaldischarge; and decode the communication based on a value of thepre-delay time.
 20. The non-transitory, computer-readable medium ofclaim 19, wherein the instructions to modify the parameter compriseinstructions to: adjust the parameter by a first value based on thevalue of the pre-delay time being in a first range; and adjust theparameter by a second value based on the value of the pre-delay timebeing in a second range.